The present invention in general relates to a surface treatment method using electric discharge, and an electrode for discharge surface treatment. More particularly, this invention relates to a technology of adhering and depositing, on the surface of a workpiece, an electrode consumed/melted material of a discharge electrode that is generated by discharge energy based on in-liquid discharge between the discharge electrode and a workpiece, thereby forming a coat of the material of the electrode on the surface. This invention also relates to an electrode for the surface treatment method using electric discharge.
The technique of adhering and depositing, on the surface of a workpiece, an electrode consumed/melted material of a discharge electrode that is generated by discharge energy based on in-liquid discharge between the discharge electrode and a workpiece, thereby forming a coat of the material of the electrode on the surface is already known (see Japanese Patent Application Laid-Open Application Nos. HEI 6-182626, HEI 9-19829, or HEI 9-192937).
In the conventional surface treatment method using electric discharge, a hard coat of metal carbide or the like is formed on a surface to be treated, exclusively in order to obtain abrasion resistance.
In general, a friction surface or a sliding surface is lubricated by fluid lubrication using a liquid lubricant such as a lubricating oil or grease.
However, in vacuum atmosphere such as a semiconductor production line or outer space, a liquid lubricant evaporates so that it cannot be used. In a high-temperature environment, such as an iron manufacturing line, a liquid lubricant also evaporates so that it cannot be used. Thus, there are many environments in which a lubricating oil cannot be used.
Particularly in a semiconductor production line, an oily lubricant present on a sliding surface causes a serious trouble in a semiconductor production process. Therefore, fluid lubrication using an oily lubricant cannot be applied thereto.
In the light of this matter, a sliding surface is coated by using a binder of a coat of a solid lubricant having self-lubricity, for example, a dicalcogen compound such as MOS2 or WS2, the so-called solid lubricant film, or by ion plating.
However, the solid lubricant film resulting from the coating method in the prior art has a drawback that the film has a restrictive life span. The ion plating has drawbacks that the device for it becomes large-sized and the size of a workpiece that can be processed is restrictive.
The present invention has been made to solve the above-mentioned problems. An object of the invention is to provide a surface treatment method making it possible to form a satisfactory and long-lived solid lubricant film on a sliding surface of a linear guide rail or the like surface without use of a large-sized device or limitation of the size of a workpiece; and a discharge electrode used in this surface treatment method.
The present invention provides a surface treatment method comprising the steps of using a discharge electrode comprising a material having solid lubricant effect to generate discharge in a pulse form between the discharge electrode and a workpiece, the surface of which is to be treated, in working liquid containing no carbon components, and adhering and depositing an electrode consumed/melted material of the discharge electrode that is generated by discharge energy based on the pulse form discharge onto a surface to be treated of the workpiece so as to form a coat having lubricant effect on the above-mentioned surface.
According to the above-mentioned method, the electrode material of the discharge electrode involving solid lubricant effect adheres and deposits, as the material having solid lubricant effect is, onto the surface to be treated without a change into a compound with carbon or the like, so that a coat having lubricity, that is, a solid lubricant film on the surface can be satisfactorily formed.
This solid lubricant film, which is different from films used in ion plating and so on, does not generate a distinct boundary which is present between the film and the base material and is a characteristic of surface treatment method using electric discharge. Inclination material property is exhibited between the film and the base material so that the film becomes a film that has strong adhesion power to the base material.
The pulse form discharge in the working liquid is performed by jetting the working liquid between the discharge electrode and the workpiece through nozzles, besides discharging electricity in a working bath in which the working liquid is stored.
The present invention also provides a surface treatment method using electric discharge wherein as the material having solid lubricant effect, there is used molybdenum, molybdenum disulfide, boron nitride, tungsten disulfide, carbon, silver, gold, lead, tin, indium, nickel, or turcite, which is a compound of carbon and fluorine.
According to the above-mentioned method, the electrode material of the discharge electrode comprising molybdenum, molybdenum disulfide, boron nitride, tungsten disulfide, carbon, silver, gold, lead, tin, indium, nickel, or turcite, which is a compound of carbon and fluorine adheres and deposits onto the surface to be treated so as to make it possible to form, on the surface to be treated, a lubricant coat (solid lubricant film) comprising molybdenum, molybdenum disulfide, boron nitride, tungsten disulfide, carbon, silver, gold, lead, tin, indium, nickel, or turcite, which is a compound of carbon and fluorine.
The present invention also provides a surface treatment method using electric discharge wherein water is used as the working liquid containing no carbon components.
According to the above-mentioned method, since water is used as the working liquid, the electrode material having solid lubricant effect adheres and deposits, as the material having solid lubricant effect is, onto the surface to be treated, without conversion of the electrode material to a compound with carbon or the like. As a result, a lubricant coat (solid lubricant film) can be formed on the surface to be treated.
The present invention also provides a discharge electrode used for carrying out a surface treatment method using electric discharge in a working liquid containing no carbon components, wherein the electrode is a powder compressed electrode obtained by compression-molding powder of molybdenum, molybdenum disulfide, boron nitride, tungsten disulfide, carbon, silver, gold, lead, tin, indium, nickel or turcite, which is a compound of carbon and flourine, or a metal electrode comprising one or more of these components.
According to the above-mentioned electrode, the electrode is formed with material like molybdenum, molybdenum disulfide, boron nitride, tungsten disulfide, carbon, silver, gold, lead, tin, indium, nickel, or turcite, which is a compound of carbon and fluorine adheres and deposits onto the surface to be treated so as to make it possible to form a lubricant coat (solid lubricant film) comprising molybdenum, molybdenum disulfide, boron nitride, tungsten disulfide, carbon, silver, gold, lead, tin, indium, nickel, or turcite, which is a compound of carbon and fluorine on the surface to be treated.